The subject of euthanasia in the biomedical research industry is not an easy one. Debates occur as to which are the preferred methods and reasons for euthanasia. Standards have been set by the American Veterinary Medical Association (AVMA) and the Canadian Council on Animal Care (CCAC) encompassing numerous points of consideration. Although most goals are met by the Research industry, a few of the goals are difficult to achieve. Such is the case with euthanizing small animals and rodents with carbon dioxide (CO2).
Various methods for euthanizing animals are known in the art, including, for example, physical methods in the form of stunning, cervical dislocation, electrocution, pithing, decapitation, shooting, maceration, microwave radiation and exsanguinations. One may also use non-inhalant pharmacological agents, inhalant anesthetics or non-anesthetic gases.
In determining the type of euthanizing process to use, individuals are urged to consider the humaneness and pain involved in the process, despite the inevitable demise of the animal. As such, a set of criteria have been set forth to be used when determining what process of euthanasia to use. The criteria include: (1) ability to induce loss of consciousness and death without causing pain, distress, anxiety, or apprehension; (2) time required to induce loss of consciousness; (3) reliability; (4) safety of personnel; (5) irreversibility; (6) compatibility with requirement and purpose; (7) emotional effect on observers or operators; (8) compatibility with subsequent evaluation, examination, or use of tissue; (9) drug availability and human abuse potential; (10) compatibility with species, age, and health status; (11) ability to maintain equipment in proper working order; and (12) safety for predators and scavengers should the carcass be consumed.
When considering the twelve criteria, many experts find that on the whole, exposure of CO2 gas to the animal is one of the more humane means euthanizing the animal. However, many research papers discussing this topic also identify a high level of distress that is prevalent with CO2-related euthanasia. Tests have been conducted on animals and humans to better understand what these levels of distress are. Although disagreement among experts exists on the exact degrees of stresses involved, euthanasia involving CO2 is still typically the preferred method for euthanizing small animals and rodents.
Carbon dioxide is preferred when euthanizing small animals and rodents because it is a relatively inexpensive gas that is colorless and odorless at low concentrations. Carbon dioxide is also considered to be quickly and readily taken into the body. Narcotic effects of CO2 are well known, but most equipment for euthanization does not properly utilize these narcotic effects of CO2 such that the euthanization can thereby be more humane and painless.
Presently, other euthanasia processes involving CO2 as the only means of euthanization have CO2 introduced at a single flow rate or at a single concentration. Such processes of introducing CO2 to an animal to be euthanized at a single flow rate, at a single concentration, or both tend to dramatically increase the stresses upon the animal and thereby make its impending death less humane and more painful. For example, studies have shown that too low of concentration of CO2 is considered a potent respiratory stimulant resulting in a tenfold increase in the ventilation rate and a feeling of profound respiratory distress.
What is desired, thus, is a means of euthanizing one or more animals using CO2 gases but also substantially limiting the physical stresses that are placed upon the one or more animals when conventionally euthanizing with CO2.